Subsurface Insulation Product and Method for Installing Same

ABSTRACT

A subsurface thermal insulation product for reducing ground disturbance during a freeze-thaw cycle comprises: a plurality of thermal insulation panels each comprising: a foam board and a water wicking sheet attached to one of the top surface or the bottom surface of the foam board. Each foam board has a top surface and a bottom surface and four peripheral shiplap edges each with a notch that permits multiple thermal insulation panels to be placed in adjacent overlapping engagement.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/441,236, filed Apr. 6, 2012, the entirety of which isincorporated by reference herein.

FIELD

The present invention relates to a subsurface insulation product thatreduces ground disturbance during freeze-thaw cycles, and a method forinstalling same to protect a road or other ground infrastructure.

BACKGROUND

Freeze-thaw cycles may result in frost heaves or frost boils, both ofwhich damage roads and other infrastructure, such as buried utilitylines,

A frost boil is caused by capillary action of water during freeze-thawcycles. The capillary action draws dirt long with the water, creating asubsurface cavity which undermines and leads to damage and ultimatelythe collapse of a road.

A frost heave is caused by absorbent soils. Soils, such as bentoniteclay, are capable of absorbing large amounts of water. As the waterfreezes it expands, pushing the soil underlying a road upwardly anddamaging the road.

One approach to reducing ground disturbances during freeze-thaw cyclesis disclosed in Canadian patent CA 2,377,702. This patent discloses amethod which includes the steps of laying a subsurface layer of thermalinsulation over an affected area, thereby thermally insulating theaffected area from freezing, and laying a subsurface layer of wickmaterial capable of drawing water away from the affected area bycapillary action parallel to the subsurface layer of thermal insulationand positioned in a path of the subsurface flow of water.

It is desirable to provide improvements to present approaches ofreducing such ground disturbances during freeze-thaw cycles.

SUMMARY

According to one aspect of the invention, there is provided a subsurfacethermal insulation product for reducing ground disturbance during afreeze-thaw cycle. The product comprises a plurality of interlockingthermal insulation panels. Each panel comprises a foam board and a waterwicking sheet attached to one of the top surface or the bottom surfaceof the foam board. Each foam board has a top surface and a bottomsurface and four peripheral shiplap edges each with a notch that permitsmultiple thermal insulation panels to be placed in adjacent overlappingengagement. The product can also include a water-repelling sheetattached to the other of the top surface and bottom surface of thethermal insulation panels; this water-repelling sheet is useful todirect water away from the panels. Each insulation panel can be composedof a foam material such as polystyrene. The insulation panel range from3″-4″ thick and the notches can extend from the side edges, i.e. have anoverlap of 2.7″ to 3.3″, and in particular have an overlap of 3″. Theratio of board thickness to overlap can be between 1.48:1 and 1.21:1 toprovide superior breakage resistance.

The thermal insulation panels are provided to reduce the likelihood offreezing in the temperature ranges at which freeze-thaw cycles normallyoccur. The wicking sheet is also provided to draw water away from theaffected area by capillary action. Thus, water is moved away from theaffected area so that there is less likelihood of ground disturbanceshould the affected area freeze.

Although beneficial results may be obtained through the use of thesubsurface insulation product as described above, water coming fromsecondary sources (such as an artisian spring) and other directions canbe confined by placing a water repelling sheet attached-bonded to theother of the top surface or the bottom surface.

Although beneficial results may be obtained through the use of thethermal insulation panel, as described above, when covering large areas,such as underlying multi-lane highways, it is difficult to do so using asingle panel. It may therefore be necessary to use multiple panels.However, the object of containing and redirecting the water could bedefeated by water seeping around the panels. It is, therefore, preferredthat the panels have notches along all four peripheral side edges toenable the insulation panels to be placed in side by side overlappingengagement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a) and (b) are end elevation views, in section, of a roadhaving with an affected area which has been repaired with a subsurfaceinsulation product according to a first embodiment (FIG. 1( a)) and asecond embodiment (FIG. 1( b)) of the invention, respectively.

FIG. 2 is a perspective view, partially cut away, of a road and aplurality of insulation panels of the subsurface insulation productaccording to the second embodiment.

FIGS. 3( a) and (b) are exploded bottom end and top end perspectiveviews of part of the first and second embodiments of the subsurfaceinsulation product.

FIGS. 4( a) to (d) are respective top plan, side elevation, bottom plan,and end elevation views of the insulation panels of the first and secondembodiments of the subsurface insulation product.

FIG. 5 is a top perspective of three adjacent insulation panels of thefirst and second embodiments of the product.

FIG. 6 is a detailed top perspective view of connections between twoadjacent insulation panels of the first and second embodiments of theproduct.

DETAILED DESCRIPTION

The embodiments of the invention described herein relate to a subsurfaceinsulation product used to reduce ground disturbance of groundinfrastructure during a freeze-thaw cycle, and a method for installingsuch a product to protect the ground infrastructure. Examples of groundinfrastructure that can be protected by the insulation product includefoundations, surface and subsurface pipelines, roadways, and sewerlines.

A first embodiment of the subsurface insulation product comprising aplurality of interlocking thermal insulation panels 13 is shown in FIG.1( a) and which is installed under a road located in a permafrost area.A second embodiment is shown in FIG. 1( b) wherein the subsurfaceinsulation product includes the thermal insulation panels 13 and angledwings 24 and which is installed in an elevated roadway. In bothembodiments, each interlocking thermal insulation panel 13 is generallyplanar and comprises a foam board 14 with means for interlocking withadjacent insulation panels 13 around all four peripheral edges of thefoam board 14, a water wicking sheet 16 attached to and covering a majorsurface of each foam board 14 and that is capable of drawing water awayfrom an affected area 12 by capillary action, and a water repellingsheet 28 attached to and covering the other major surface of each foamboard 14 and that provides a water incursion barrier. As will bedescribed in further detail below, the position of the water wickingsheet 16 and water repelling sheet 28 when installed in the ground isdependent on the direction in which the water or moisture originates.

In the second embodiment shown in FIGS. 1( b) and 2, the insulationpanels 13 are installed under an elevated roadway and interlock with aplurality of downwardly angled wings 24. The downwardly angled wings 24prevent frost penetration from peripheral edges 26 of the insulationproduct, When this embodiment is installed in the manner as shown inthese Figures, the panels 13 are oriented so that the water wickingsheets 16 are positioned in a path of the subsurface flow of water. Inthis case, the water wicking sheets 16 are facing upwards and coveringthe top surface of the foam board 14 and the water repelling sheets arecovering the bottom surface of the foam board 14. Soil 10 is thenreplaced over the water wicking sheets 16. After the soil 10 isreplaced, the affected area 12 can then be repaved with travel surface18. In operation, the water wicking sheets draw water originating fromthe source of water above the subsurface insulation product 100 andtowards the foam board 14; this water then flows along the foam board 14to its edges and then is directed by the water repelling layer 28 to adrainage area away from the roadway 18.

The subsurface insulation product will now be described in greaterdetail with reference to FIGS. 3( a)-(b) to 5. Both embodiments of theinsulation product comprise panels 13 having a generally planarthermally insulating foam board 14 sandwiched by one or more of thewater wicking sheets 16 and one or more of the water repelling sheets28. In the second embodiment, the product also includes one or morethermally insulating angled wings 24.

Each foam board 14 is in the form of a single rigid planar andrectangular board. The foam board 14 can be composed of high densityexpanded polystyrene (EPS), such as the closed cell EPS foam insulationsheets made by Plasti-Fab™ under the trade-mark PlastiSpan®. This EPSfoam insulation sheet meets or exceeds the requirements of the Canadianstandard CAN/ULC-S701-05 Standard for Thermal Insulation Styrene, Boardsand Pipe Covering. Other suitable foam sheets include high strength EPSfoam insulation boards manufactured by Beaver Plastics™ under thetrade-mark Terrafoam HS-40® also meets or exceeds CAN/ULC S-701 type 2standard as well as the ASTM C-578 Type 14 standard by the AmericanSociety for Testing and Materials. Other suitable foam sheets 14 areprovided by Dow under the SM™ and SM Hi Load™ trade-marks.Alternatively, the foam board 14 can be made from another insulatingfoam material such as polyurethane.

In this embodiment, each foam board 14 is about four feet (4′) wide byeight feet (8′) long by four inches (4″) thick; however, the foam board14 can be produced in other dimensions depending on the preferences ofthe user. For example, the board 14 can be between 3″ to 4″ thick, Thefoam board 14 has a top surface 124 and a bottom surface 126 and fournotched or “shiplap” peripheral edges, namely, first and second opposedshort shiplap edges 120, 121, and third and fourth opposed long shiplapedge 122, 123. The first short shiplap edge 120 has a notch extendingoutwardly from the bottom half of the edge 120 and along its entirelength. The second short shiplap edge 121 has a notch extendingoutwardly from the top half of the shiplap edge 121 and along its entirelength. Similarly, the third long shiplap edge 122 has a notch extendingoutwardly from the bottom half of the shiplap edge 122 and along itsentire length, and the fourth long shiplap edge 123 has a notchextending outwardly from the top half of the edge 123 and along itsentire length. The net impression created by these four shiplap edges isof two offset sheets that are fused together, as evident from theFigures, even though the board 14 is made from a single piece.

While the foam board 14 is formed by extruding a single piece ofpolystyrene material and cutting the four notched shiplap edges 120,121, 122, 123 into the board 14 in the configuration described above,the foam board 14 can be alternatively formed from a pair of sheets (notshown) joined together in an offset manner.

In this embodiment, the notches for the first and second short shiplapedges 120, 121 and the third and third long shiplap edges 122, 123extend 3″ (about 75 mm) outwards and 4 feet along the length of therespective shiplap edges 120, 121, i.e. has a 3 inch “overlap”. Thisoverlap dimension has been found to provide superior resistance tobreakage relative to the material and dimensions of the sheet 118,particularly the sheet's thickness. It is expected that an overlap ofbetween 2.7″ and 3.3″ (about 70 and 85 mm) for a 4 inch thick EPS foamboard 14 (and each notch being ½ the thickness of the board at 2″) willprovide similar superior breakage resistance. To put it another way, anEPS board 14 should have a ratio of board thickness to overlap ofbetween 1.48:1 and 1.21:1 to provide superior breakage resistance.

The notched shiplap edges 120, 121, 122, 128 allow each thermalinsulation panel 13 to overlap or “interlock” with adjacent andsimilarly configured thermal insulation panels 13. Referring to FIG. 5as an example, the second short shiplap edge 121 of a first foam board(shown as 14(a) in this Figure) can mate with the first short shiplapedge of a second foam board (shown as 14(b) in this Figure), and thefourth shiplap edge 123 of the first thermal insulation panel 13(a) canmate with the third shiplap edge of a third foam board (shown as 14(c)in this Figure).

Referring again to FIGS. 3( a) and (b), the water wicking sheet 16 ismade of a non-woven geosynthetic fabric which is capable of drawingwater away from an affected area by capillary action is attached to andcovers the top surface 124 of the foam board 14 and extends slightlypast the first short shiplap edge 120. The water repelling sheet 28 ismade of a woven geosynthetic fabric which is attached to and covers thebottom surface 126 of the foam board 14, such as woven geosyntheticfabric 9852 manufactured by Nilex™. Each of these sheets 16, 28 can beattached by staples, or by an adhesive such as a foam adhesive such asthose manufactured by 3M™. Attaching these sheets 16, 28 to the board 14significantly enhances the tensile and shear strength of the panel 13.

It will be appreciated that depending on whether the source of wateroriginates above or below the level of the insulation panel 13, thewater repelling sheet 28 could be attached to the top surface 124, andthe non-woven wicking sheet 16 could be attached to the bottom surface126 instead of as illustrated.

When the thermal insulation panels 13 are interlocked, the subsurfaceinsulation product is formed which provides a comprehensive thermal andmoisture barrier and which is resistant to breakage due to its robustnotched shiplap edges.

Referring to FIGS. 1( b) and 2, one method of reducing grounddisturbance during freeze-thaw cycles using the second embodiment of thesubsurface insulation product includes excavating soil 10 from anaffected area 12 that has been affected by ground disturbance due tosubsurface flow and subsequent freezing of water. A plurality of theinsulation panels 13 are then laid over the affected area 12, therebythermally insulating the affected area 12 from freezing. Referring toFIG. 1( b), the surface of the board 14 having the wicking sheet 16attached thereon is laid in a path of the subsurface flow of water. Thefoam board in each insulation panel 13 is provided to reduce thelikelihood of freezing in the temperature ranges at which freeze-thawcycles normally occur. The wicking sheet 16 of each insulation panel 13serves to move water away from the affected area 12, so that there isless likelihood of ground disturbance should affected area 12 freeze.

While the above description has applied to installing the subsurfaceinsulation product to protect ground infrastructures in areas havingseasonal zones, the insulation product 100 can also be useful to protectground infrastructure used in permafrost areas, namely to protect groundinfrastructure from damage caused by permafrost thaw.

Such ground infrastructure includes gas production equipment on awellsite (not shown). A method of installing the subsurface insulationproduct in such a permafrost wellsite is now described. First, the siteis covered by bedding material (typically snow) to provide a uniformsurface for laying down the thermal insulation panels 13. The side canbe sloped downwards on about a 2% grade from the wellhead (not shown) toaccommodate drainage. Then, the modular thermal insulation panels 13 areapplied and interlocked together such that the panels 13 extend slightlybeyond the desired protected zone. Then, appropriate cover such asfrozen soil or plywood is added over the subsurface insulation product.The product will remain in place for the duration of the drilling andfor resource extraction. Once the well is shut in, the top-fill isremoved and the product can be extracted for reuse at other well sites,leaving the present site in a remediated state.

A method of installing the subsurface insulation product in a permafrostsite having a surface pipeline is now described (but not shown). Such aninstallation avoids the use of refrigeration units on supportfoundations, which can drastically reduce operation and capital costs.The support foundation is installed by: (1) anchoring the foundationthen excavating the piling area to the permafrost level, (2) installingthermally insulated pilings, (3) installing the subsurface insulationproduct by laying and interlocking the thermal insulation panels 13 overthe permafrost soil (4) forming and pouring a concrete foundation, then(5) backfilling the perimeter of the foundation with native material. Apipeline corridor is installed by (1) stripping soil to the frost line,(2) installing the subsurface insulation product by laying andinterlocking the thermal insulation panels 13, and then (3) replacingthe surface soil. Use of the insulation product under the entire lengthof an elevated pipeline will allow the elevation of the pipeline to besubstantially reduced as it will insulate the permafrost from heatradiated from the line load.

A method of installing the subsurface insulation product in a permafrostsite having subsurface pipelines is now described (but not shown).First, a trench is excavated in conventional fashion to a level ofpermafrost soil. The insulation product is installed in the mannerdescribed above at the bottom of the trench. The sub-surface pipeline isthen laid in a conventional manner and the trench is partiallybackfilled, conformed to the shape of the sloped insulation panels. Moreinsulation product is laid on top of this partially backfilled material.Then the trench is completely backfilled and the process is completed.

A method of installing the subsurface insulation product in a permafrostsite having a roadway is now described and shown in FIG. 1( a). First,overburden is removed until permafrost 11 is exposed. Then theinsulation product is installed over the permafrost 11 in the mannerdescribed above. Then the insulation product 100 is covered with nativesoil fill 10. Finally, normal roadway construction procedures areundertaken to complete the roadway 18.

In this patent document, the word “comprising” is used in itsnon-limiting sense to mean that items following the word are included,but items not specifically mentioned are not excluded. A reference to anelement by the indefinite article “a” does not exclude the possibilitythat more than one of the element is present, unless the context clearlyrequires that there be one and only one of the elements.

It will be apparent to one skilled in the art that modifications may bemade to the illustrated embodiment without departing from the spirit andscope of the invention as hereinafter defined in the Claims.

1-7. (canceled)
 8. A method for protecting ground infrastructure on apermafrost area from permafrost thaw, comprising: (a) covering apermafrost site with a bedding material such that a uniform surface isformed over the permafrost site; (b) laying a plurality of thermalinsulation panels over the bedding material, wherein each panelcomprises a foam board, each foam board having a top surface and abottom surface and four peripheral shiplap edges each with notch thatpermits multiple thermal insulation panels to be placed in adjacentoverlapping engagement; and a water wicking sheet attached to one of thetop surface or the bottom surface of the foam board; (c) interlockingthe panels together such that at least one panel is interlocked withfour other panels around its four peripheral shiplap edges; and (d)applying a covering material over the interlocked panels; then (e)installing ground infrastructure over the covering material.
 9. A methodas claimed in claim 8 wherein the bedding material is snow.
 10. A methodas claimed in claim 8 wherein each panel further comprises a waterrepelling sheet attached to the other of the top surface or bottomsurface of the foam board.
 11. A method as claimed in claim 8 whereinthe ground infrastructure is gas production equipment on the permafrostsite. 12-13. (canceled)
 14. A method of protecting a roadway in apermafrost site from permafrost thaw, comprising: (a) removingoverburden to a level of permafrost soil; (b) laying a plurality ofthermal insulation panels over the permafrost soil, wherein each panelcomprises a foam board, each foam board having a top surface and abottom surface and four peripheral shiplap edges each with a notch thatpermits multiple thermal insulation panels to be placed in adjacentoverlapping engagement; and a water wicking sheet attached to one of thetop surface or the bottom surface of the foam board; (c) interlockingthe panels together such that at least one panel is interlocked withfour other panels around its four peripheral shiplap edges; and (d)covering the interlocked panels with a selected covering material; then(e) constructing a roadway on the covering material.